1. Field of the Invention
The present invention relates to a quantum computer and a quantum computing method utilizing coupling of an optical resonator and atoms.
2. Related Art
In recent years, research of the quantum computer has been performed vigorously. As a method for implementing the quantum computer, a method of preparing a plurality of physical systems each having three states in an optical resonator, utilizing two lower stable states as quantum bits, and coupling spatially distant physical systems via photons in the optical resonator is proposed (see, for example, JP-A 2001-209083 (KOKAI)). In JP-A 2001-209083 (KOKAI), quantum bits are distinguished with an optical frequency by utilizing the fact that the frequency difference between two lower states differs according to the individual physical system. And the state is operated by utilizing two-photon resonance. If the frequency difference between the lower states is different according to the individual physical system, therefore, two-photon resonance occurs in only one physical system and the physical system is operated thereby. It thus becomes possible to selectively operate an individual physical system by setting an optical frequency.
Especially in the nuclear spin state of ions doped into crystal, decoherence is very slow. Therefore, a solid-state quantum computer utilizing an energy level (hyperfine level) which depends upon the nuclear spin of ions as the quantum bit and utilizing its inhomogeneous broadening in quantum bit selection is being considered. Since in general the inhomogeneous broadening of the hyperfine level is not so wide, however, it becoming an obstacle to increasing the number of quantum bits is regarded as a problem.